[jdt-dev] Null Annotations / EEA

["Jan N. Klug" <jan.n.klug@xxxxxx>]

Good evening,

you may know that there is a project named LastNPE that provides EEA for a bunch of libraries.

Recently a discussion was brought up how to correctly model the annotations for methods like Optional.orElse or Map.computeIfAbsent

In both cases we need to make the return value @Nullable, because the argument is allowed to be null and in that case the return value is also null.
However this creates the need for a lot of unnecessary null-checks, if the value is guaranteed to be non-null, e.g. if used like Map.computeIfAbsent(key, k -> new Foo()).

So what we would need to have is something to express „same nullness like argument“ (like @PolyNull in checkerframework) or the option to have two annotations, one for a @Nullable argument and one for a @NonNull argument. Both need support in the compiler.

That‘s why I‘m writing here. I couldn’t find a discussion for that. WDYT?

Jan (GitHub: J-N-K)